Feasibility is examined for a hand-held instrument to measure thrust force and joint motion during spinal manipulation and rehabilitation of patients with neuromuscular or musculoskeletal disorders such as low back pain. Application to the health field: provide non-invasive monitoring and control of forces applied during physical rehabilitation procedures for the back. This instrumentation is expected to promote patient safety, especially those at risk for stroke. It offers a tool for clinical research into efficacies of spinal rehabilitation and fundamental neuroscience research into back pain mechanisms. Specific aims and methods for Phase 1 are, 1) evaluate with oscilloscope and select appropriate force and acceleration transducers; 2) characterize accelerometer output from thrusting instrument, body surface, and vertebral bone of animal model (dog); 3) construct and calibrate prototype instrument for doctor's office; 4) computer calculates displacment from accelerations; determine force-displacement curves for selected vertebrae. Phase 2 would further characterize motion behavior of the entire spine, establish safe thrust limits, and to relate mobilization to clinical improvement. Phase 2 would also involve instrument package miniaturization and automation for commercialization. There is strong commercial potential because few objective measures are available in this field, and the market includes chiropractic, physical therapy and physical medicine.